1. Field of the Invention
The invention relates to improvements in strain mechanisms as used on bandmills, particularly bandmills as used in the lumber processing industry.
2. Prior Art
A bandmill has an endless saw running on spaced co-planar wheels, the wheels being journalled on arbors, the saw being strained by forcing the arbors apart. A common means to strain the saw uses a deadweight lever mechanism in which a weighted counterweight arm, through a knife-edge system, exerts an axial force on a strain rod, the strain rod acting indirectly on one of the arbors, tending to force the arbors apart. This system has been used with success for many years, but fluctuations in the cutting load produce excessive tension in the saw such that life of the saw is reduced, and quality of cutting is impaired. Excessive tension results from slow response of the strain system to accommodate rapidly applied additional forces on the saw resulting from, for instance, lateral deflection of the saw, such slow response being attributed to friction occuring between the knife-edges and knife-edge seats, and inertia of the weighted lever arm. Undesirable effects of friction and inertia are accentuated in high strain bandmills.